When asked about her favourite Vogue covers, she told Allen: "Quite often the ones I really like are the creative, arty ones. But they don't sell as well.

"It's a real balancing act doing a magazine, between creativity and sales.

"If I knew exactly what sold it would be like having the secret of the universe, but I'd say broadly speaking, if you're going to talk about a model or a personality, it's kind of a quite middle view of what beauty is.

"Quite conventional, probably smiling, in a pretty dress; somebody looking very 'lovely'. The most perfect girl next door."

She added: "People always say 'why do you have thin models? That's not what real people look like' But nobody really wants to see a real person looking like a real person on the cover of Vogue.

"I think Vogue is a magazine that's about fantasy to some extent and dreams, and an escape from real life.

"People don't want to buy a magazine like Vogue to see what they see when they look in the mirror. They can do that for free."

When asked if she was tired of having to defend Vogue and the fashion industry from critics, she said: "I guess a certain amount of defending comes with the job.

"The magazine does really well, so obviously some people like it and it's not a real problem.

"I get fed up with having to deal with the question of why are models thin, that sort of bores me, but that's the only thing really."

Shulman has previously argued for the "insane" tiny sizing of designer samples to be changed, and has encouraged discussion about body image at the annual Vogue Festival.

"I do think the designers should cut bigger and use bigger models on the catwalk," she said. "I've said it again and again.

"But there is much more diversity than there used to be, it is changing."

The current edition of Vogue features television chef Nigella Lawson on the cover, who was praised for her "natural" look.